We have developed and characterized the only myelogenous leukemia cell line (K-562) available in culture, originally derived from a patient with CML. The K-562 has the Philadelphia (Ph1 ion) chromosome after 8 years in culture. It has been extensively examined and found to be free of virus and mycoplasma, does not have T- or B-cell markers but does have Fc receptors. These cells, when injected into rabbits, monkey, or goat, elicit the production of specific antibody which demonstrates complement-mediated cytotoxicity for K-562 and leukemic cells of patients with leukemia. Specificity for myelogenous leukemia cells is obtained after absorption of antisera with normal peripheral leukocytes and bone marrow cells as well as with leukemia cells of others types (i.e., AML, ALL, CLL). The purpose of this project is: 1) to refine our fractionation procedures to isolate the target antigen of K-562 cells recognized by goat monospecific immunoglobulins; 2) to determine definitively if the target antigen reactive with antibody is the same or different from that recognized by human natural killer cells; 3) to assess the presence of immune complexes in the sera of patients with leukemia and to characterize the components of such complexes; 4) to study the potential for differentiation of K-562 cells with known inducers of murine leukemia cells such as dimethylsulfoxide and sodium butyrate; and 5) to use the immunologic reagents (monospecific globulins and characterize antigens) as reference standards to accurately detect incomplete remission and early relapse in patients with leukemia.